Vehicle hoists are widely used at gasoline stations, repair garages and the like wherever service is customarily performed on the underside of a roadway vehicle. Such hoists are commercially available from a variety of manufacturers, and while they may differ in detail from one manufacturer to another, they generally consist of a super structure including a bolster or a pair of bolsters to which arms or wheel tracks are attached for underlying support of a vehicle. Exemplifying adjustable arm-type support structures in a vehicle lift are the disclosures of U.S. Pat. Nos. 3,080,018 and 2,878,897.
The individual arm-type unit has long been a preferred choice for general garage automotive service in that it leaves the vehicle wheels suspended and therefore accessible for maintenance while being of a relatively low cost construction compared to other types of available units. Typically, the arm-type unit includes four arms in which the inboard end of each is pivotally connected and retained via a transverse pin in a more or less horizontal plane. The pivot pin customarily extends into a base plate supported on the hoist mechanism while a cover plate overlying the arm end cooperates with the base plate to define a pivot cavity of predetermined height therebetween. The cavity is preferably sized to closely accommodate the thickness of the received swivel arm so as to permit free horizontal swivelling of the arm without binding. A problem with such cavities, however, has been the dimensional clearance variation between the opposing faces defining the cavity and the swivel arm received therein resulting from expected mill tolerances or wear. Whatever the cause, insufficient clearance can produce binding and damage while excessive clearance results in undue sag at the distal end of the arm. Uncontrolled and/or differential sag variation in the individual arms can in turn result in imperfect and undesirable canting of a vehicle in the course of being lifted. The prior solution for overly thin arms has been to shim the arm while excessively thick arms have required machining or replacement.
Despite recognition of the foregoing, a ready solution has not heretofore been known.